Beam shaping assembly for neutron capture therapy

• US 9,974,979 B2
• Filed: 05/06/2015
• Issued: 05/22/2018
• Est. Priority Date: 12/08/2014
• Status: Active Grant

• Current Assignee: Neuboron Medtech, Ltd.
• Original Assignee: Neuboron Medtech, Ltd.
• Inventors: Liu, Yuan-Hao, Lee, Pei-Yi
• Primary Examiner(s): Stoffa, Wyatt
• Assistant Examiner(s): CHOI, JAMES J
• Application Number:
  US14/705,811
• Publication Number:
  US 20160158579A1
• Time in Patent Office: 1,112 Days
• Field of Search: None
• CPC Class Codes: A61N 2005/109 Neutrons
• CPC Class Codes: A61N 2005/1094 Shielding, protecting against radiation
• CPC Class Codes: A61N 2005/1095 Elements inserted into the radiation path within the system, e.g. filters or wedges
• CPC Class Codes: A61N 5/1077 Beam delivery systems
• CPC Class Codes: G21G 4/02 Neutron sources
• CPC Class Codes: G21K 1/10 Scattering devices; Absorbing devices; Ionising radiation filters
• CPC Class Codes: H05H 3/06 Generating neutron beams targets for producing nuclear reactions H05H6/00; neutron sources G21G4/02
• CPC Class Codes: H05H 6/00 Targets for producing nuclear reactions supports for targets or objects to be irradiated G21K5/08 ; preparation of tritium C01B4/00; targets, e.g. pellets for fusion reactions by laser or charged particles beam injection H05H1/22

Abstract

A beam shaping assembly for neutron capture therapy includes a beam inlet, a target having nuclear reaction with an incident proton beam from the beam inlet to produce neutrons forming a neutron beam defining a main axis, a moderator adjoining to the target, a reflector surrounding the moderator, a thermal neutron absorber adjoining to the moderator, a radiation shield arranged inside the beam shaping assembly and a beam outlet. The neutrons are moderated to epithermal neutron energies. An outer surface of the moderator includes at least a first tapered section. The reflector leads the neutrons deviated from the main axis back. The thermal neutron absorber is used for absorbing thermal neutrons so as to avoid overdosing in superficial normal tissue during therapy. The radiation shield is used for shielding leaking neutrons and photons so as to reduce dose of the normal tissue not exposed to irradiation.

Claims

1. A beam shaping assembly for neutron capture therapy comprising:

a beam inlet;

a target, wherein the target has nuclear reaction with an incident proton beam from the beam inlet to produce neutrons, and wherein the neutrons form a neutron beam defining a main axis;

a moderator adjoining to the target, wherein the neutrons are moderated by the moderator to epithermal neutron energies, and wherein an outer surface of the moderator includes a first tapered section and a second tapered section adjoining to the first tapered section, and a tapering direction of the first tapered section is opposite to a tapering direction of the second tapered section;

a reflector surrounding the moderator, wherein the reflector leads the neutrons deviated from the main axis back to enhance epithermal neutron beam intensity;

a thermal neutron absorber adjoining to the moderator, wherein the thermal neutron absorber is used for absorbing thermal neutrons so as to avoid overdosing in superficial normal tissue during therapy;

a gap channel arranged between the moderator and the reflector, wherein the gap channel is an empty area devoid of solid materials and allows neutron beams to pass for enhancing epithermal neutron beam intensity, and wherein the gap channel is enclosed by the reflector, the moderator and the thermal neutron absorber;

a radiation shield arranged inside the beam shaping assembly, wherein the radiation shield is used for shielding leaking neutrons and photons so as to reduce dose of the normal tissue not exposed to irradiation;

an air passage, arranged between the thermal neutron absorber and the beam outlet and enclosed by the thermal neutron absorber, the reflector and the radiation shield; and

a beam outlet,

wherein all of the beam inlet, the moderator and the beam outlet are extended along the main axis;

wherein the first tapered section includes a first side and a second side, is tapered in a first direction away from the beam outlet and tapering from the second side towards the first side, and the second tapered section includes a third side and a fourth side and is tapered in a second direction toward the beam outlet and tapering from the third side towards the fourth side, and

wherein the first side and the second side are disposed on a coned-shaped tapering surface of the first tapered section and the third side and the fourth side are disposed on a tapering surface of the second tapered section.

2. The beam shaping assembly for neutron capture therapy according to claim 1, wherein the beam shaping assembly is further used for accelerator-based boron neutron capture therapy.

3. The beam shaping assembly for neutron capture therapy according to claim 2, wherein a proton beam is accelerated by means of an accelerator to overcome coulomb repulsion energy of a target atomic nucleus and generate nuclear reaction with the target to produce neutrons, and the target is made of a metal material.

4. The beam shaping assembly for neutron capture therapy according to claim 1, wherein an epithermal neutron energy range ranges from 0.5 eV to 40 keV, a thermal neutron energy range is below 0.5 eV, and a fast neutron energy range is above 40 keV, and the beam shaping assembly reduces the quantity of thermal neutrons and fast neutrons;

and wherein the moderator is made of a material having a cross section for principally acting with fast neutrons but hardly acting with epithermal neutrons, the reflector is made of a material having a high neutron reflection ability, and the thermal neutron absorber is made of a material having a cross section for acting with thermal neutrons.

5. The beam shaping assembly for neutron capture therapy according to claim 4, wherein the moderator is made of at least one of D₂O, AlF₃, CaF₂, Li₂CO₃, MgF₂ and Al₂O₃.

6. The beam shaping assembly for neutron capture therapy according to claim 4, wherein the reflector is made of at least one of Pb or Ni.

7. The beam shaping assembly for neutron capture therapy according to claim 4, wherein the thermal neutron absorber is made of ⁶Li.

8. The beam shaping assembly for neutron capture therapy according to claim 1, wherein the radiation shield includes a photon shield and a neutron shield.

9. The beam shaping assembly for neutron capture therapy according to claim 1, wherein the target is perpendicular to the main axis.

10. The beam shaping assembly for neutron capture therapy according to claim 1, wherein the target is arranged into the first tapered section.

11. The beam shaping assembly for neutron capture therapy according to claim 3, wherein the target is made of ⁷Li and has ⁷Li (p, n)⁷Be nuclear reaction with the incident proton beam from the beam inlet to produce neutrons.

12. A beam shaping assembly for neutron capture therapy comprising:

a beam inlet;

a target made of ⁷Li, wherein the target has ⁷Li (p, n) ⁷Be nuclear reaction with an incident proton beam from the beam inlet to produce neutrons, and wherein the neutrons form a neutron beam defining a main axis;

a moderator adjoining to the target, wherein the neutrons are moderated by the moderator to epithermal neutron energies and wherein an outer surface of the moderator includes a first tapered section and a second tapered section adjoining to the first tapered section, and a tapering direction of the first tapered section is opposite to a tapering direction of the second tapered section;

a reflector surrounding the moderator, wherein the reflector leads the neutrons deviated from the main axis back to enhance epithermal neutron beam intensity;

a thermal neutron absorber adjoining to the moderator, wherein the thermal neutron absorber is used for absorbing thermal neutrons so as to avoid overdosing in superficial normal tissue during therapy;

a gap channel arranged between the moderator and the reflector, wherein the gap channel is an empty area devoid of solid materials and allows neutron beams to pass for enhancing epithermal neutron beam intensity, and wherein the gap channel is enclosed by the reflector, the moderator and the thermal neutron absorber;

a radiation shield arranged inside the beam shaping assembly, wherein the radiation shield is used for shielding leaking neutrons and photons so as to reduce dose of the normal tissue not exposed to irradiation;

an air passage, arranged between the thermal neutron absorber and the beam outlet and enclosed by the thermal neutron absorber, the reflector and the radiation shield; and

a beam outlet,

wherein all of the beam inlet, the moderator and the beam outlet are extended along the main axis;

wherein the first tapered section includes a first side and a second side, is tapered in a first direction away from the beam outlet and tapering from the second side towards the first side, and the second tapered section includes a third side and a fourth side, and is tapered in a second direction toward the beam outlet and tapering from the third side towards the fourth side, and

wherein the first side and the second side are disposed on a coned-shaped tapering surface of the first tapered section and the third side and the fourth side are disposed on a tapering surface of the second tapered section.

13. The beam shaping assembly for neutron capture therapy according to claim 12, wherein at least a part of the beam inlet is received into the moderator.

14. The beam shaping assembly for neutron capture therapy according to claim 13, wherein the moderator comprises a recess for receiving the target and at least a part of the beam inlet.

15. The beam shaping assembly for neutron capture therapy according to claim 14, wherein the reflector comprises a recess for receiving the other part of the beam inlet.

16. A beam shaping assembly for neutron capture therapy comprising:

a beam inlet;

a target, wherein the target has nuclear reaction with an incident proton beam from the beam inlet to produce neutrons, and wherein the neutrons form a neutron beam defining a main axis;

a moderator adjoining to the target, wherein the neutrons are moderated by the moderator to epithermal neutron energies and wherein an outer surface of the moderator includes a first tapered section and a second tapered section adjoining to the first tapered section, and a tapering direction of the first tapered section is opposite to a tapering direction of the second tapered section;

a reflector surrounding the moderator, wherein the reflector leads the neutrons deviated from the main axis back to enhance epithermal neutron beam intensity;

a thermal neutron absorber adjoining to the moderator, wherein the thermal neutron absorber is used for absorbing thermal neutrons so as to avoid overdosing in superficial normal tissue during therapy;

a gap channel arranged between the moderator and the reflector, wherein the gap channel is an empty area devoid of solid materials and allows neutron beams to pass for enhancing epithermal neutron beam intensity, and wherein the gap channel is enclosed by the reflector, the moderator and the thermal neutron absorber;

a radiation shield arranged inside the beam shaping assembly, wherein the radiation shield is used for shielding leaking neutrons and photons so as to reduce dose of the normal tissue not exposed to irradiation;

an air passage, arranged between the thermal neutron absorber and the beam outlet and enclosed by the thermal neutron absorber, the reflector and the radiation shield; and

a beam outlet,

wherein the first tapered section includes a first side and a second side, is tapered in a first direction-away from the beam outlet and tapering from the second side towards the first side, and the second tapered section includes a third side and a fourth side, and is tapered in a second direction toward the beam outlet and tapering from the third side towards the fourth side, and

wherein the first side and the second side are disposed on a coned-shaped tapering surface of the first tapered section and the third side and the fourth side are disposed on a tapering surface of the second tapered section.

17. The beam shaping assembly for neutron capture therapy according to claim 16, wherein the beam inlet is extended into the moderator and the target is arranged into the moderator for enhancing the epithermal neutron beam intensity.